User's Manual

AC65/AC75 Hardware Interface Description

Confidential / Preliminary

AC65/AC75_hd_v00.372 Page 49 of 118 2006-08-03

3.6 Power Saving

Intended for power saving, SLEEP mode reduces the functionality of the AC65/AC75 to a

minimum and thus minimizes the current consumption. Settings can be made using the

AT+CFUN command. For details see [1]. SLEEP mode falls in two categories:

• NON-CYCLIC SLEEP mode: AT+CFUN = 0

• CYCLIC SLEEP modes, AT+CFUN = 7 or 9.

The functionality level AT+CFUN=1 is where power saving is switched off. This is the default

after startup.

NON-CYCLIC SLEEP mode permanently blocks the serial interface. The benefit of the

CYCLIC SLEEP mode is that the serial interface remains accessible and that, in intermittent

wake-up periods, characters can be sent or received without terminating the selected mode.

This allows the AC65/AC75 to wake up for the duration of an event and, afterwards, to

resume power saving. Please refer to [1] for a summary of all SLEEP modes and the

different ways of waking up the module.

For CYCLIC SLEEP mode both the AC65/AC75 and the application must be configured to

use hardware flow control. This is necessary since the CTSx signal is set/reset every 0.9-2.7

seconds in order to indicate to the application when the UART is active. Please refer to [1] for

details on how to configure hardware flow control for the AC65/AC75.

Note: Although not explicitly stated, all explanations given in this section refer equally to

ASC0 and ASC1, and accordingly to CTS0 and CTS1 or RTS0 and RTS1.

3.6.1 Network Dependency of SLEEP Modes

The power saving possibilities of SLEEP modes depend on the network the module is

registered in. The paging timing cycle varies with the base station. The duration of a paging

interval can be calculated from the following formula:

t = 4.615 ms (TDMA frame duration) * 51 (number of frames) * DRX value.

DRX (Discontinuous Reception) is a value from 2 to 9, resulting in paging intervals from

0.47-2.12 seconds. The DRX value of the base station is assigned by the network operator.

In the pauses between listening to paging messages, the module resumes power saving, as

shown in Figure 10.

Figure 10: Power saving and paging

The varying pauses explain the different potential for power saving. The longer the pause the

less power is consumed.

0.47-2.12 s

0.47-2.12 s 0.47-2.12 s

Paging

Power Saving